Effect of Rounding Side Corners on Vortices Shedding and Downwash from Square Cylinder of Finite Length Placed on a Ground Plane.

Abstract

This paper describes the effect of rounding side corners on vortices shedding and downwash from a square cylinder of finite length placed on a ground plane. The experiment was carried out in an N.P.L blowdown-type wind tunnel with a working section of 500 mm × 500 mm × 2000 mm in size at the Reynolds number 1.25 × 104 and 2.5 × 104. The power spectrum, autocorrelation and velocity were measured, and the Strouhal number was determined. The two types of vortices shed from a square cylinder with rounded side corners have also been observed. As a result, it was found that ( i ) the vortices shed from a cylinder are arch vortices for H/D = 2, which change into Karman vortices at H/D=4∼7 ; (ii) the decay of shedding vortices and turbulent eddies becomes fast and the average scale of turbulent eddies decreases as rounding of the side corners increases : (iii) the downwash from the free end weakens as rounding of the side corners increases.